The endoscope is generally designed so as to be inserted into a body cavity of human body in order to perform the observation, examination, diagnosis and treatment of the body cavity of human body. The endoscope is generally constituted by a flexible inserting tube which is designed to be inserted into a body cavity, and a manipulation portion which is provided at a proximal end portion of this flexible inserting tube for manipulating a distal end portion of this flexible inserting tube so as to enable this distal end portion to bend. Further, this endoscope is also provided with a light guide flexible tube which is extended from the manipulation portion and connected with a light source device and a control device.
The flexible inserting tube is constituted by a flexible tube portion which is excellent in flexibility enabling it to follow up with the curvature of body cavity as this flexible tube portion is inserted into a curved body cavity, and a curved portion which is contiguously provided at a distal end of this flexible tube portion and can be optionally bent through the manipulation thereof.
Incidentally, this flexible inserting tube is provided therein with various members such as a bending mechanism for bending the curved portion existing at a distal end portion of the inserting tube, a light guide for transmitting light from a light source to the distal end portion of the inserting tube, an image guide for transmitting an image of a subject to the manipulation portion, a tube for introducing forceps to be employed in performing, for example, the treatment and cellular examination, an air/liquid feeding tube for enabling the injection of a medical liquid, etc., these members being disposed to extend longitudinally as required.
When these flexible tube portion and curved portion are caused to bend, friction is caused to be generated among various members that have been built in these flexible tube portion and curved portion, resulting in the generation of pressure acting on these members. Therefore, with a view to minimize these friction and pressure, a lubricant is applied to the outer circumferential wall of each of these members.
In order to prevent the infection to a patient or an operator, it is indispensable to apply a disinfection or sterilization treatment to the flexible tube portion and the distal end portion, which have been inserted into a curved body cavity, after the use thereof. Therefore, according to the prior art, gas such as ethylene oxide gas (hereinafter referred to as EOG) or a liquid disinfectant has been employed for the sterilization.
However, since EOG is toxic in itself and hence presents the problem of residual toxicity, the aeration of the flexible inserting tube is required to be performed for removing EOG, thus raising a problem that it takes a long time for the sterilization treatment of the flexible inserting tube. Namely, there is a problem that the aforementioned gas sterilization is expensive in running cost.
On the other hand, the latter sterilization treatment using a liquid disinfectant is also accompanied with problems that it may not be possible to secure sufficient sterilization effects and that it involves complicated administration of the liquid disinfectant. Additionally, there is a problem of how to handle the waste liquor thereof, thus raising the problem of increase in cost for the waste disposal that is required for obviating the problem of environmental pollution that may be caused by the waste liquor.
Because of these reasons, it is now desired to apply the high-pressure/high-temperature steam sterilization that has been conventionally employed for the sterilization of medical instruments. This high-pressure/high-temperature steam sterilization is advantageous in various aspects that since water is employed for the sterilization, the problem of residual toxicity can be obviated, that it is possible to secure strong sterilizing effects, that the time required for the sterilization treatment is relatively short, that the running cost for the sterilization can be saved, and that there is no possibility of generating waste liquor.
However, in this high-pressure/high-temperature steam sterilization, steam is permitted to permeate through various materials of the components constituting the endoscope, such as rubber, macromolecular material such as plastics, adhesive, etc. Therefore, when the endoscope which is conventionally constructed into a water-tight structure is placed in a high-pressure/high-temperature steam sterilization apparatus and subjected to sterilization treatment, there may be raised a problem that the steam is permitted to permeate even into the interior of the endoscope that has been constructed into a water-tight structure by the ordinary method using an O-ring, an adhesive, etc.
Further, on the occasion of high-pressure/high-temperature steam sterilization, it has been generally practiced to place the endoscope in a high-pressure/high-temperature steam sterilization apparatus in such a manner that the interior of endoscope is kept communicated with the exterior thereof in order to prevent fracture of the sheath of the curved portion of endoscope. On this occasion, high-pressure/high-temperature steam is permitted to enter into the interior of endoscope, thus causing a light guide fiber bundle formed of a bundle of a large number of glass fibers to contact with this high-pressure/high-temperature steam, occasionally resulting in the damage to the light guide fiber bundle or in the damage to the lubricity thereof.
More specifically, in the case of the conventional endoscope, molybdenum disulfide is employed as a solid lubricant to be interposed between a protective tube for covering the light guide fiber bundle and a sheath tube. Therefore, when this molybdenum disulfide is caused to contact with the high-pressure/high-temperature steam, this molybdenum disulfide may be aggregated and adhered to these tubes or oxidative degradation of molybdenum disulfide may be caused to occur, thus causing the generation of sulfurous gas or the generation of cracks in the rubber sheath tube, occasionally resulting in the breakage of fibers.
Meanwhile, it is also desired to apply a peroxide-based sterilization method, e.g., a hydrogen peroxide low temperature plasma sterilization method to the endoscope. This hydrogen peroxide low temperature plasma sterilization method is advantageous in that it is not only possible to perform the sterilization treatment at normal temperature and under a low humidity but also possible to greatly minimize the generation of residual matters and secondary products after the sterilization, thus making it excellent in safety.
This hydrogen peroxide low temperature plasma sterilization method however is accompanied with a problem that free radicals such as hydroxyl radical, super-oxide, hydroxyperoxy radical, etc., are caused to be generated together with plasma in the sterilization apparatus, thereby permitting these free radicals to permeate through various materials of the components constituting the endoscope, such as rubber, macromolecular material such as plastics, adhesive, etc.
Furthermore, in the case of this hydrogen peroxide low temperature plasma sterilization method, for the purpose of more completely sterilize the interior of channel tube to be used for feeding air, a so-called booster which is formed of a vessel filled with a small amount of hydrogen peroxide is connected with the channel tube and this hydrogen peroxide is permitted to inject therefrom into the channel tube as a negative pressure is created therein. On this occasion however, this hydrogen peroxide is permitted to enter into the endoscope.
As in the case of the aforementioned high-pressure/high-temperature steam sterilization, these hydrogen peroxide and free radicals may become a cause for the oxidative degradation of molybdenum disulfide which is employed as a solid lubricant to be interposed between a protective tube and a sheath tube, thereby generating sulfurous gas or cracks in the sheath tube made of silicone rubber and disposed inside the protective tube, occasionally resulting in the breakage of fibers.
As described above, the sterilization treatments may become a cause for the denaturing or degradation of the lubricant, the degradation of lubricity or the breakdown of the endoscope.
The present invention has been made in view of overcoming the aforementioned problems and hence, the purpose of the present invention is to provide an endoscope which employs a solid lubricant which is capable of withstanding the sterilization treatments to be performed according to the high-pressure/high-temperature steam sterilization method or the hydrogen peroxide low temperature plasma sterilization method.